Food storage containers, conventionally of an appropriate plastic or synthetic resinous material such as polypropylene, are frequently also used as convenient containers for the heating or reheating of foodstuffs within a microwave oven. However, in order to accommodate the buildup of internal pressures during heating, the seal of the container must be removed or at least partially released. Complete removal of the seal is often not desirable because of potential spillage problems, an exposure of other goods within the oven to fumes emitted from the container stored goods, and the like.
Similarly, a partial opening of the seal, normally by an upward stripping of one section of the frictionally engaged edge flange, is inexact, particularly when dealing with round containers and seals, and could lead to an accidental release of the entire seal as a result of internal pressures.